Blender 2.8 Import Function does not find .obj or .ply file for import
Dragging it into Blender won't help, as Blender's drag and drop handling doesn't auto-check the file type and apply the relevant importer (unfortunately!).

It's possible that when you select Import > Wavefront (.obj) the file is being filtered out of the view for some name-based reason. You can disable filtering in the top right corner to view all files without extension filtering.



If none of that works and the importer is having some problem with the actual file, you'll get some sort of error message in the system console. But it doesn't sound like you've got that far yet.

"trying to open that file directly with Blender even causes Blender to CTD with no error message."
That one would be a bug, then. It should be able to notice that you're trying to use Open on something that's not a .blend file and not crash, but it seems you have discovered a case where that isn't happening.